Inside an optical device provided in an image-forming device based on an electrophotographic system, such as a copy machine or a laser beam printer, optical elements, such as mirrors, and lenses, are held in prescribed positional relationships with a light-generating device, and other optical components.
One method of holding optical elements at prescribed positions inside an optical device is, for example, a method in which the optical elements are held between a biasing means, such as a board spring and a supporting member.
Patent Document 1 describes a holder for an elastic supporting member [40] that holds a prescribed edge of a mirror [29], the front and back surfaces of which are parallel, and fixes the mirror to a fixed member of an optical device that uses the mirror [29] as a reflecting surface. The elastic supporting member [40] includes a roughly U-shaped elastic member [41] that holds the prescribed edge of the mirror [29] with spring characteristics, and spherical weight parts that are provided on the upper and lower areas of the roughly U-shaped elastic member [41] and face and abut the front and back surfaces of the mirror [29].
In the abovementioned holding structure, depending on the arrangement of the optical elements, there are cases in which an equilibrium cannot be obtained in the force applied to the optical elements and distortion occurs in the optical elements due to the effects of moment. For example, in Patent Document 1, when the optical elements are arranged with a tilt relative to the elastic supporting member [40], a balance between the forces applied to the mirror [29] from the upper and lower weight parts cannot be maintained (refer to FIG. 4(a) in Patent Document 1). In this case, it is possible that distortion may occur in the mirror [29] due to the effects of rotational moment.